The typical perception of Bob Ewell by readers of Harper Lee's novel To Kill a Mockingbird is one of hatred. Now, that is the typical modern reaction to Ewell. If the question were to be posed during the period which Lee wrote the novel (in 1960), readers may have a very different perspective.
In 1960, many people were still harboring prejudices against people of color. Therefore, some (during this period in time) would have felt like raising up Bob Ewell for enacting his hatred for African Americans upon Tom Robinson.
Today, many people look at prejudices as something worth being frowned down upon. Therefore, many people would believe that Bob Ewell got what was coming to him (his death).
Unfortunately, there are still places in society today where prejudice runs rampant. Readers of To Kill a Mockingbird may agree with the mindset of those who openly fought against equality for all races.
Based upon all of this, to denote how one perceives Bob Ewell after reading his testimony, one must consider what (if any) prejudices they harbor. An individual reader can only name how they feel about Bob Ewell for him or her self.